Radio operated positioning control system



April 16, 1946. H- J. FINISON 2,398,419

RADlO` OPERATED POSITIONING CONTROL SYSTEM y I Filed Aug. 17, 1943 a Tl 'eva/v www Aap. dni/6. 65N.

TES

AENT

RADIO OPERATED POSITIONING CONTROL SYSTEM Harvey J. Finison, Dayton, Ohio Application August 17, 1943, Serial No. 498,975

4 Claims.

(Cl. Z50-2) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to radio operated positioning control devices and relates in particular t to a type of such control wherein the element to be controlled may be displaced an amount equal or proportional to the displacement of a control element at the remote controlling station.

Many radio remote control devices have been proposed in the prior art in which the position of the controlled object such as an aircraft elevator or ships rudder could be displaced from a neutral position to any one oi a limitednumber of predetermined positions by coded impulses or by selected transmission frequencies operating selector relays, but such systems require a large amount of receiving apparatus4 if the number of controlled object positions is increased. It has further been proposed to establish position of the controlled object by variation in the time or successive number of impulses transmitted, which has the disadvantage that the rate of response is slow and uncertainty exists as to exactly what position the controlled object is in at the cessation of signal transmission unless a complicated answer-back apparatus is employed to transmit a signal indicative of the position of the controlled object to the remote transmitting station.

In accordance with the present invention a. continuous radio signal is transmitted from the control station, and its frequency is varied in either sense from a standard frequency to cause deflection of the controlled element in a corresponding sense from the neutral position. A radio receiver picks up the transmitted control signal and feeds the amplified output to a discriminating network which is operative to control a sensing relay to energize power means for positioning the controlled object, the discriminating network being such that the unbalance thereof operative to energize the sensing relay is a function of the variation in the transmitted frequency from the predetermined value. Means are provided responsive to the position of the controlled object from a predetermined or neutral position to cancel the effect of the unbalance of the network and to alter the balance point so that it corresponds to the new value of the transmitted frequency so that the power means is deenergized when the controlled object has been displaced an amount proportional to the change in frequency of the transmitted wave so that the position of the controlled object is always positively determined and no further operation of the power positioning means will take place as long as the frequency of the transmitted signal remains unchanged. By means of this system of control, the primary control element at the transmitting station can be operative to vary the transmitted signal frequency from the predetermined value in accordance with the displacement of the control element from a neutral position, and the controlled object will 5 be correspondingly displaced from the neutral position with a rapidity dependent only on the power available for positioning purposes.

The principal object'of the invention is to provide a radio remote control device including a transmitting and receiving station such that variation in the frequency of control signals transmitted from the transmitting station from a predetermined frequency will cause a positioning of a controlled object at the receiving station in a direction and amount corresponding in the direction and amount of the change in frequency of the transmitted signal from the predetermined value.

Another object of the invention is the provision in a radio remote control system of a transmitter adapted to have the frequency of the signal radiated thereby varied above or below a predetermined value, a remote receiver adapted to receive the transmitted signal, a frequency difference responsive network adapted to be selectively unbalanced by the output of said receiver upon a variation in the received signal frequency from said predetermined value, a relay selectively actuated by the unbalance of said network, power operated positioning means controlled by said relay, and means including a follow-up connection with said positioning means for restoring the balanced condition of said network at the new value of the transmitted frequency when the controlled object has been positioned at a desired po n 4 Other objects of the invention will become apparent by reference to the detailed description hereinafter given and to the appended drawing in which: y

Fig. l is a schematic illustration of one form of the invention; and

Fig. 2 is a diagrammatic illustration of a modified discriminating circuit network for use in the system of Fig. 1.

Referring now to Fig. 1, the reference numeral i generally indicates an adjustable frequency signal generator which may, for example,v comprise a conventional audio frequency oscillator, the frequency of which maybe adjusted by variation of the inductance or capacity of the resonant circuit in a manner well-known in the art, the adjustable frequency control being adapted to be actuated by means of a shaft 2 rotated by a gear 3 fixed thereon 4and in turn Amoved by a rack 4 which may be connected byl means of a lever 5 mounted on a rock shaft 6 which is actuated by a primary control element l such as to simulate the control stick of an aircraft. By movement of the control element 1 in either direction from a neutral position. the frequency the output the signal generator I mayl be either increased or decreased from a predetermined value veorresponding to the neutral position oi the control element 1.v 'I'he output of the signal lgenerator 1` I is fed to a conventional radio transmitter such that the carrier wave output of the transmitter is modulated by theoutput of the adjustable frequency signal generator I, the modulation of the carrier wave preferably being at an audio frequency. The output of the radio transmitter 8 is fed to a conventional antenna 8 for radiation into space. It is thus seen that as the control element 1 is moved in either direction from a neutral position, the modulation of the carrier I located at Vthe remote station, which'isled to a conventional radio receiver II, in which'the modulated component of the carrier wave transarmature' circuit ci' the" motor 42.v 'I'he electromagnetic clutch 41, which may be ofv any wellknown type, is adapted, upon the passing of current therethrough upon energizing of the motor 42,`to run in either direction to connect the armature of the motor to a shaft 49 to rotate the same in the same sense as the rotation of the motor, and upon the deenergizing of the motor will cause an uncoupling of the shaft 48 from the motor 42, this arrangement being provided so that overrunning of 'the motor 42 will have no eiect upon causing further positioning of the shaft 49, and

thereby hunting is eliminated. The shaft 48 is provided with a Worm 50'which is adapted to engage a worm gear sector 4I which is rotatably mounted as at 52 and connected by means of an arm 53 to move a controlled object 54 whichmay be an aircraft control surface, ships rudder, or

mitted from antenna 9 ls detected and amplified in s. manner well-known lin the art, the output of the receiver II being impressed on the primary coil I2 of a transformer generally indicated by the reference numeral I3. The transformer I3 is provided with two secondary coils I4 and I5 respectively, each of which formsa part of. the separate discriminating circuit as will now be described. The transformer secondary I4 has one side thereof connected in series with a variable condenser I8, and the terminals of the secondary I4 are connected across a load resistor Il, and the side thereof containing the condenser is connected to the' grid 20 of a vacuum tube 22. In similar fashion the transformer secondary I5v has one side thereof connected in series with an inductance I1 and connected to a grid 2| of a vacuum tube 23, a load resistor I8 being shunted across the output terminals of the secondary Il beyond the inductance I1, and the load resistors I8'and ISbeing connected together to a conveni tional c battery ,34 which` supplies s biasing potential on the grids 28 and 2 I vof the Avacuumtubes 22 lanrl 23 such that they are biased at or near thecut ofi' point.l A conventional A and B battery supply 32 suppliesythe necessary current to the, filament and plate circuits of the vacuum A tubes 22 and 28. The plates 24 and 25 of the respective vacuum tubes 22 and 23 are connected the like. Rotation of shaft 49 in`either direction will causea displacement of the controlled object 54 in a corresponding direction from a neutral position.

"As previously noted, the condenser I8 was indicated as being a variable condenser, and reduction gearing generally indicated by the reference numeral 55 is provided to be driven by the shaft 49 and terminatesin an output shaft 55 which ls adapted to be connected to the variable condenser I8 so as to change thesetting thereof, the reduction gearing 55 and shaft 58 forming what is known in the art as a follow-up connection.

'Ihe circuit including the Atransformer secondary I4, condenser I8, load resistor I8 and vacuum `tube 22 forms a discriminating circuit in which the voltage appearing on the grid 28 of vacuum tube 22 is a function of the frequency of the current induced in the transformer secondary I4.

The voltage appearing across load resistor I8, and

by means of conductors 28 and 21 to the coils 28 andk 29 of a differential relay generally indicated by the reference numeral 3II, the relay- 38 including a rocking armature 35 provided with a contact arm upon which is mounted a central conl tact 36 suitably biased by springs to a normal neutral position and the contact 36 being adapted 'to engage either of a pair of oppositely spaced motor controlling contacts 31 and 38 respectively, which are connected by means of conductors 39 and respectively to the iield coils of a conventional'split field reversible electric motor 42. A battery 44 supplies current by means of conductor 45 to the central contact 36 and is connected by means of a conductor 48 in series with a conventional electromagnetic clutch 41 which is connected in series by means of conductor 48 to the transformer secondary I5,

hence the voltage on grid 20, will depend on the reactance in the branch of the circuit containing the condenser I8. The condenser I8, since it is variable, will pass currents of higherv frequency more readily than currents of lower frequency, depending upon its adjusted capacity value; i. e., the capacitive reactance increases as the frequency is reduced from the value corresponding to the present value of the capacity, and the capacitive reactance decreases for higher frequen.

the circuit including load resistor I9, and

c ies. AThe conditions for lnductance I1 is the converse of the above in that the voltage across the load resistor I9 and appearing on grid 2| will depend on the reactance of inductance I1, which will increase as the frequency of the currents passing therethrough increases and will decrease its reactance as the current frequency is reduced.

For each setting of the condenser I8, between predetermined limits, there will be one value of current frequency for which the reactances of both circuits will be alike, and under which conditions the voltages on the grids of Vacuum tubes 22 and 23 will be equal, and therefore the currents fed to relay coils 28 and 28 will be equal and the relay armature 35 will remain in its neutral position. If the frequency of the modulated vcomponent of. the carrier wave-received on antenna I 0 is increased above the rpredetermined value for which the reactancesfof the discriminating circuits are f equal', then; the circuit including "transformer-secondary I 4 :and ,condenser I5 will :controlled object 56 will cease.

that a denite change in frequency of the output accesso ing on grid 2li; will exceed the voltage occurring on grid si and will cause an imbalance of the currents supplied to relay coils 2u and 2t, resulting. in the armature et being attracted towards the relay coil 28, which will cause the central motor controlling contact 3e to engage the contact 3B to energize the motor d! to run in one direction, causing a displacement of the controlled object such as the aircraft control surface 54 vin a corresponding direction from the neutral position. As the motor t2 continues to operate, the reduction gearing 55 Will rotate shaft 5% in such a direction that the capacity oi condenser IB will be so altered that the capacitive reactance of the circuit including the said condenser will be brought into equality with the inductive reactance ofthe circuit including transformer secondary i5 and inductance i1, and when equality of the reactance of the circuits is again established, the voltages on' grids 20 and 2| will again be the same, and the relay armature 35 will return to the neutral position and deenergize motor 62 and simultaneously declutch the motor by means of electromagnetic clutch el from driving relation with shaft e9 so that further positioning of the It is thus seen of radio receiver ii from a predetermined frequency willcause a corresponding proportional deflection of the controlled object 5B, and the bvlously if the structure at the receiving staw tion is properly arranged and tuned, the freduency corresponding to the neutral position oi the controlled object 5t may be made to match exactly the frequency-of the signal generator iwhen the control element 'l is in a corresponding neutral position, and by movement of the control element l in one direction from said neutral position, the frequency of the signal generator l may, for example, be reduced in an amount proportional to the deflection of the control member l from the said neutral position, which in turn will cause e. corresponding change in the frequency of the output of the radio receiver il at the remote station which, through the discriminating circuits, will then set motor @2 into operation to position the controlled object Se an amount proportional to the deflection of the primary control member l from the neutral position, and in a similar fashion deection of the control member 'l in the opposite sense will cause a corresponding defiection of the controlled object from a neutral position.

It will be seen from the above that an operator vat a remote transmitting station may operate a control element and have a corresponding deflection of a controlled object at a remote point,

, and the system at the remote station is such that discriminating circuits will be brought into balance such that their neutral or balance frequency corresponds to the value of the received output irequencyappearing on transformer primary i2. The entire system then being in equilibrium, nothing further will happen until the received frequency appearing on transformer primary coil i2 is further altered. c

An exactly opposite effect will take place if the frequency of the receiver output appearing on the transformer primary coil l2 is decreased from a predetermined value, corresponding to the neutral position of primary control element l, since in this case the reactance, of the inductivey reactance circuit including inductance il will be decreased from the value of the capacitive reactance and the voltage on grid El will exceed the voltage appearing on grid 20, causing the difierential relay Bilto operate in the opposite sense and cause through operation'of-motor e2 a deflection of the controlled object 56 in the reverse sense from that as described above. Also the follow-up eiect derived from rotation of shaft es will vary the capacity of variable condenser i@ in the opposite sense such that the capacitive reactance thereof will be decreased until a balance is again eected between the two discriminating circuits, and further operation oi motor d2 will then cease inthe same manneras above described, QItisthereiore'seen that the conmary coil l2 from a predetermined value. In other Words, for every value of received frequency, there is a corresponding position of the controlled object 5e, and the controlled object will be moved from whatever position it should then happen to have unt-il the same has reached the said corresponding position, and when in such position the equilibrium value of thevidlscriminating circuits will be brought into coincidence with the received frequency appearing on the transformer primary coil i2 and all further positioning will cease.

vtrolled object 5S- may b e made tofollow any l change in'received frequency appearing on pri' upon the controlled objecil reaching the desired position, the servo mechanism actuating the same will be deenergized. It is then immaterial for what length of time the same signal is transmitted, since no further change in the position of the controlled object will ensue; but as soon as the position of the controlling element l is' changed the mechanism at the remote station will cause movement of the controlled object until the same is brought into a corrpondlngi or proportional psition. AIt is obvious that in the operation of this system` coded signals or transmission of signals for predetermined intervals of time are knot required and the operator can operate the \ment 1,. rudder pedals'or the like, so as to render the control ofv anr aircraftvor ,ship at a remote point exactly the same as if the controlled element were directlyA actuated by the primary control element l or equivalent control means.

It is seen that upon unbalance of the equilibrium frequency of the discriminating circuits, the'servomotor t will be energized to run in either of two directions tov cause the displacement of the controlled object, andat the same time the motion of the control object is feeding back through the follow-up mechanism, to bring the reactance values of the discriminating circuits again into balance, andthis balance frequency will in all cases correspond to the modulation frequency of the then transmitted signal as modulated by the signal generator l; that is, the equtlibrium value` of the discriminating circuits will always tend to approach the value of the fre` quencyof signal generator i, and by this means proportional movement of the controlled object is assured.,` y

1t is obvious that the discriminating circuits i1- lustrated and described with reference to Fig. l,

while operating purely on change of react-ance, have somewhat the characteristics oi' filter circuits so that in lieu thereof actual frequency responsive tuned filters may be employed to actuate the relay It and sucha modincation of the discriminating circuit of the device of Fig. 1 is illustrated in Fig. 2. Referring now to Fig. 2, the

output of the radio receiver I l is led by means of` conductors 58 into parallel connected conductors 59, the output of which is led to filters 60 and 6I. 'I'he nlter 60, for example, may be made adjustable as to the frequency which it will pass and.

recnly by means of conductors ze and 21 to the differential relay. for operation pf. the same to control the servo mechanism of Fig. 1 in the same manner as previously described. Upon the receiving of a signal by the receiver i I the amplified output thereof will be fed to the respective filters G and 6I, and if diilerlng from the then adjusted value for balance, will cause differential relay It to operate in one direction or the other depending upon whether the change in frequency is above or below the value for balance existing just prior to the receiving of the signal; that is, if the frequency is increased, relay coil 28 will have a predominating effect, while if thefrequency is decreased, relay coil 29 will have a predominating efi'ect. By means ofthe follow-up connection 56 the equilibrium value between the filters and El can be so adjusted that the equilibrium value will always tend to become equal to the transmitted signal frequency of the signal generator of Fig. l, and accordingly this system will also operate to effect the same resultsas the device of Fig. 1 and may be bodily inserted therein in place of the discriminating circuit arrangement shown therein.

rWhile the system above described with reference to Fig. 1 has been disclosed as employing an audio frequency modulated carrier wave, it is obvious that the frequency of the carrier wave itself may be altered directly and a frequency modulated receiver employed in place of. the radio receiver i I, and in using this system the results will be identical to that as described above since the loutput of the receiver i i can be made to vary in frequency in the same manner as if an audio frequency modulation of the carrier wave had been employed, and the discriminating circuits will operate in the same manner as previously described.

It will be further apparent with respect'to the device illustrated in Fig. l'that in place of employing a variable condenser I6 actuated by the follow-up shaft 56, thesame result can be attained by making the condenser I6 of fixed capacity and varying the inductance I1, the inwithout departing from the spirit of the invention as described in the appended claims.

I claim:

1. A radio controlled device for positioning a controlled object in response to a change in frequency of a signal transmitted from a remote point comprising a radio receiver responsive to the transmitted signal, the output of said receiver changing in frequency proportionalto the change in frequency of the transmitted signal, a frequency responsive discriminating network connected to the output of said receiver, a differential relay operated by the output of said network, said network being normally'balanced and operative upon a change in frequency to actuate the relay in a sense depending on the direction of they change in frequency from the then existing balanced condition, reversible servo mechanism adapted to be selectively energized by said relay, a controlled object positioned by said servo mechanism, adjustable balancing means associated with said network, and a follow-up connection between said servo mechanism and said adjustable balancing means operative to work into balance with the frequency of the transmitted signal upon the servo mechanism positloning the controlled object in a predetermined position, whereby balancing of said network willl cause said differential relay to deenergize said servo mechanism.

2. The structure as claimed in claim l, in which said network includes two reactive circuits conl nected to the output of said receiver, the reactance of one of said circuits being capacitativev and the reactance of the other circuit being inductive, and kmeans for varying the reactance of one of said circuits whereby the equilibrium frequency for balance between said circuits may be altered between predetermined limits. v

3. The structure as claimed in claim 1, in which said frequency responsive network comprises a pair of tuned filter circuits normally balanced such that each will pass currents of a predetermined frequency but respectively reject currents having a frequency greater and less than said i predetermined frequency and means for varyingv the tuning of one of said filters so that the equi- A librium frequency of said network may be varied ductance varying means being actuated by the follow-up shaft 56, and in fact, where very low audio frequencies are employed, this mode of operation might be preferable to that illustrated ln the drawing. f

It will be apparent to those skilled in the art that many changes may be made in the form :of the invention as illustrated and described, and

.between predetermined limits.

4. A radio controlled device for positioning a controlled object in response to change in fre" quency between predetermined limits in signals transmitted from a remote point, comprising a radio receiver responsive to the transmitted signals, a frequency responsive discriminating network connected to the output of said receiver, a relay connected to the network and operated by unbalance of the electrical condition thereof upon a change in the frequency of the transmitted signals, servo mechanism for positioning a controlled object and selectively'controlled by said relay, a follow-up'drive actuated by said servo mechanism, mechanically adjustable means form-*iv ing part of said networkfor altering the electrical balanced condition thereof and a connectionbetween said follow-up drive and said mechanically adjustable means, said follow-up drive causing a change in the balance frequency of said network which causes the balance frequency to attain a value equal or proportional tothe frequency of the transmitted signals.

HARVEY J. manson.

bring said net- 

